Selecting and grafting wild Pinus monophylla on containerized Pinus edulis rootstocks

摘要

Single-leaf pinyon pine (Pinus monophylla) is a source of wild-collected, edible, soft-shelled pine nuts that are in great demand. This project identified high yielding, wild trees and evaluated two means of grafting the selections to Pinus edulis rootstocks to establish a stock block.Trees were selected and sampled from productive wild stands near Hamlin Valley (February 23, 2018), Eureka (March 5, 2018), and the Raft River Mountains (February 12, 2018), UT and Austin, NV (February 2, 2018). These stands were identified by pine nut collectors and represent a broad sample from the Great Basin. From each stand, six trees were selected based on visual observations of the number of cones in the tree and on the ground.Cone production was quantified by collecting six upper-canopy shoots from the top half of each tree at six compass points (N, NE, SE, S, SW, NW) and counting abscission scars from the past 10 years. Analysis of the cone scar data showed that some trees were more productive than others both within andbetween stands. The three most productive trees with the highest quality scion wood in each stand were selected for use in grafting. Scion wood was collected concurrent with shoots for cone scar analysis and from the same branches.Second year seedlings of P. edulis (Pitkin Forest Nursery, University of Idaho) were used as rootstocks. Seedlings were delivered in November 2017, potted into 4-inch x 4-inch x 12-inch pots with a bark-based mix (Metro-Mix 900) and kept above freezing temperatures in a cold frame to prevent dormancy. Scion wood was stored for one week after collection at 4°C before grafting. A total of 24 scions from each mother tree were grafted, with 12 side-wedge grafts and 12 side-veneer grafts with one graft per.root-stock.Side-wedge grafts consisted of scion wood cut in a V-shape and inserted into a corresponding cut extending into the stem about one-third of the stem diameter. Side-veneer grafts consisted of scion wood cut shallowly along one side and notched at the bottom.